By Tom Skilling
August has been bathed in sunshine and warm across the Chicago area. But rainfall has been incredibly scarce.
The month has tallied just 40 percent of its normal precipitation -- 1.8 inches vs. 4.48 inches.That's a stunning turnaround from the heavy rains of June with 6.17 inches of rain and July with 8.84 inches of rain. The same period a year ago produced more than two times as much rain (4.26).
But while beautiful, the dry spell has occurred in a period of the year during which sunlight is strong and evaporation rates are high. In the 38 days since this area's last drenching rains -- the 6.44 inches which fell at O'Hare and 7.06 at Midway between July 22 and 25 -- more than 8 inches of water has evaporated from area soils. The ground is cracked at some locations and vegetation is showing the stress of the lack of moisture.
But it's a situation which may finally turn around in coming days.
The same southerly winds which are predicted to propel Tuesday's high temperatures to 90-plus degrees for the 21st time this year will transport tropical moisture into the area. That moisture is expected to fuel thunderstorm development late Tuesday night and in clusters Wednesday and a portion of Thursday.
Computer rainfall projections in coming days are eye-catching, ranging from as little as 0.21 inches to as much as much as 3 inches. Ten of the most recent 12 computer model estimates of rainfall exceed 1 inch. With 2 inches of moisture predicted to evaporate into the atmosphere Wednesday and Wednesday night, instability growing and a powerful jet stream settling into Chicago's airspace from Montana and the Dakotas, the potential for repetitive, sometimes thundery downpours will increase. That can lead to this area's most impressive precipitation tallies.
Books about to close on an August running 6 degrees warmer than '09
Temperature trends suggest air conditioners have hummed 80 percent more frequently than a year ago this month and 90 percent more often during summer as a whole. The predicted 92-degree high Tuesday would mark this month's sixth day at 90 degrees or higher. The month managed just one 90-degree reading a year ago
Hurricane Earl has Mid-Atlantic/Northeast nervous
Hurricane Earl grew into an extremely dangerous Category 4 hurricane just north of the Leeward Islands Monday as its sustained winds hit 135 mph. The storm moves over warm 86-degree waters Tuesday -- a development which may foster further intensification. The storm is on a path which is likely to carry it precariously close to the East Coast.
Rip tides generated along the Eastern Seaboard by distant Earl as well as Hurricane Danielle have resulted in two deaths in recent days and swimmers are being discouraged from heading too far out in the water at beaches up and down the Atlantic Coast.
Earl's projected path would take the storm over or just off North Carolina's Outer Banks Friday and then push the system northward paralleling the Mid-Atlantic and New England coasts. Any westward jog in its path could expose the region's coastline more directly to the winds, waves and squalls in time for the early part of the Labor Day weekend.
Cooler water north of the Carolinas is likely to lead to at least a moderate reduction in Earl's top winds, but the storm is expected to maintain hurricane force (74-plus mph) velocities as it races north into Canada's Maritime Provinces Saturday.
Tropical forecasters are warning all with travel plans in the area to keep up with updates on Earl's strength and movement.
Record rains drench Montana ahead of autumn chill
Rains and high winds swept sections of Montana in the midst of record low daytime temperatures Monday. The day's high failed to break above 48 at Lewiston and 46 at Sanford, where a record 1.4 inches of rain fell. Colder air is expected to support mountaintop snows above the 8,000-foot level
